Before 1963, poliovirus vaccine produced in the United States was contaminated with simian virus 40 (SV40), which causes cancer in animals. To examine whether early-life SV40 infection can cause human cancer, the authors studied 54,796 children enrolled in the US-based Collaborative Perinatal Project (CPP) in 1959-1966, 52 of whom developed cancer by their eighth birthday. Those children whose mothers had received pre-1963 poliovirus vaccine during pregnancy (22.5% of the children) had an increased incidence of neural tumors (hazard ratio = 2.6, 95% confidence interval: 1.0, 6.7; 18 cases) and hematologic malignancies (hazard ratio = 2.8, 95% confidence interval: 1.2, 6.4; 22 cases). For 50 CPP children with cancer and 200 CPP control children, the authors tested paired maternal serum samples from pregnancy for SV40 antibodies using a virus-like particle enzyme immunoassay and a plaque neutralization assay. Overall, mothers exhibited infrequent, low-level SV40 antibody reactivity, and only six case mothers seroconverted by either assay. Using the two SV40 assays, maternal SV40 seroconversion during pregnancy was not consistently related to children's case/control status or mothers' receipt of pre-1963 vaccine. The authors conclude that an increased cancer risk in CPP children whose mothers received pre-1963 poliovirus vaccine was unlikely to have been due to SV40 infection transmitted from mothers to their children.
